Transient bone marrow edema in renal transplantation: a distinct post-transplantation syndrome with a characteristic MRI appearance.

We describe four patients who developed severe knee pain within 3 months of renal transplantation. Plain radiographs were normal and inflammatory markers (CRP, ESR) were all within normal ranges. Magnetic resonance imaging (MRI) showed a distinctive pattern in all four cases of bone marrow signal changes, extending from the epiphyseal region into the metaphyseal region in two cases. The appearances were different from those of avascular necrosis (AVN) and reflex sympathetic dystrophy and showed no progression to develop AVN during the follow-up period of 36 months. In all cases the pain resolved over a period of 3 months without specific therapy. Follow-up MRI scans were obtained in all patients after the pain had subsided, which revealed resolution of the MRI changes. We suggest that MRI be the investigation in such patients and that bone marrow edema changes will regress without the need to withdraw cyclosporin.